There has recently appeared a mobile phone provided with an FM transmitter which transmits FM radio waves from an antenna. When music data stored in the mobile phone is reproduced and the resultant signals are transmitted from the FM transmitter on FM radio waves via the antenna, a radio receiver can receive the signals for audio output.
On the other hand, the mobile phone is provided with a connection terminal for connecting to an earphone, a connection terminal for connecting to a USB device such as a personal computer, and a connection terminal for connecting to a battery charger, whereby the mobile phone is connected with an external device such as an earphone, a USB device, or a battery charger. When the mobile phone is connected with an external device, however, antenna gain of the antenna to which the FM transmitter is connected changes, which may cause the field intensity of the FM radio waves transmitted from the FM transmitter to exceed a predetermined value. The FM transmitter has conventionally been configured not to transmit FM radio waves while an external device is connected to the mobile phone.
This however poses a problem that a user cannot talk using an earphone, communicate with a personal computer, or charge a battery while replaying music using the radio receiver.